title: On the strongly correlated electron hydride Ce2Ni2MgH7.7.
abstract: The intermediate valence compound Ce 2Ni 2Mg absorbs irreversibly hydrogen when exposed under 1 MPa of H 2 pressure at room temperature. The resulting hydride Ce 2Ni 2MgH 7.7 is stable in air and crystallizes as the deuteride La 2Ni 2MgD 8 in a monoclinic structure (space group P2 1 /c) with the unit cell parameters a = 11.7620(2), b = 7.7687(2), and c = 11.8969(2) A and beta = 92.75 degrees . The H-insertion in Ce 2Ni 2Mg induces a structural transition from a tetragonal to a monoclinic symmetry with an unit cell volume expansion Delta V m/ V m approximately 24.9%. The investigation of the hydride by magnetization, electrical resistivity, and specific heat measurements indicates a change from an intermediate valence behavior to a non-magnetic strongly correlated electron system. This transition results from a change of the coupling constant J cf between 4f(Ce) and conduction electrons induced by the hydrogenation.
authors.affiliation: CNRS, Université de Bordeaux, ICMCB, 87 avenue du Docteur Albert Schweitzer, 33608 Pessac Cedex, France. chevalier@icmcb-bordeaux.cnrs.fr
authors.forename: Bernard
authors.initials: B
authors.lastname: Chevalier
authors.forename: Aleksandra A
authors.initials: AA
authors.lastname: Krolak
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Bobet
authors.forename: Etienne
authors.initials: E
authors.lastname: Gaudin
authors.forename: François
authors.initials: F
authors.lastname: Weill
authors.forename: Wilfried
authors.initials: W
authors.lastname: Hermes
authors.forename: Rainer
authors.initials: R
authors.lastname: Pöttgen